1. Field of the Invention
This invention relates to wheel axle bearing retaining means for a railway truck having pedestal-type frames.
2. Description of the Prior Art
In a railway truck having a pair of pedestal type side frames supported on the wheel axles through roller or cartridge type axle bearings carried within inverted U-shaped pedestal jaws provided in the side frames, it is necessary to entrain the bearings within the jaw to limit their vertical movement relative to the side frames. This is particularly important if a railway car derails to minimize the danger zone surrounding the wreck by preventing the car's wheel and axle assemblies from flying free of the car. Additionally, by insuring that the wheel axles remain secured to their respective car trucks, structural damage to the car is minimized.
In the past, a variety of structures have been developed to entrain the bearings within the truck side frames. For example, one means has been to provide a horizontally extending rigid retaining bar beneath each bearing. The respective ends of the bar are secured or entrained by the opposing lower pedestal jaw portions. One end of the retaining bar is pivotally entrained on one side of the pedestal jaw and its other end is secured to the other side of the jaw with bolts or similar means. See U.S. Pat. Nos. 1,724,798; 2,424,327; and 3,110,269.
Although a side frame incorporating rigid retaining bars does entrain the axle bearings within the side frame jaws, the manner in which the retaining bar is secured by the jaws substantially limits its useful service life. More particularly, the rocking of a moving railway car will cause downward oscillatory impact loading by the bearing on the retainer bar. This causes the bar to tend to pivot about its pivoted end and to stretch and loosen the bolt securing the other end of the bar. Consequently, since once the bolt is stretched it is generally impossible to tighten it to resecure the bar, it is necessary to discontinue use of the car until the bolt or both the bar and bolt are replaced. Clearly, during the useful life of a rail car this can result in a substantial maintenance expense and increased costs associated with the non-availability of the car.
Another means of restraining vertical movement of an axle bearing has been to secure a cantilevered key-type retaining member in one of the pedestal jaw portions with a bolt or similar means. See U.S. Pat. Nos. 1,229,617 and 3,091,192. This design provides for the key member to extend partially beneath the bearing to entrap it within the downwardly opening or inverted U-shaped jaw. However, during extended use the key must endure substantial bending as well as shear loads which are imposed on the key-type retainer by the downward oscillatory movement of the bearing. Such loading on the key-type retainer could result in it being bent to such an extent that it becomes wedged in the jaw and therefore difficult to remove for repair or replacement as well as stretching and consequently loosening the bolt which secures the retainer to the jaw portion.
U.S. Pat. Nos. 253,439 and 1,640,180 illustrate bands for securing the axle bearings in the jaws. The band in the U.S. Pat. No. 253,439 is secured by a pin at one end and a bolt at the other end which pass through aligned apertures in the frame and strap which weaken the strap. In U.S. Pat. No. 1,640,180 a resilient strap is used which at its ends is secured by transverse pins to the spaced jaw elements which may easily shake loose and provide a construction imposing high stresses in the areas of connection of the pins to the ends of the strap. The strap is thin and lays against the external side of the frame.
In addition to the above, vibration of the trucks during normal rail operations tends to loosen the bolts securing either the retaining bar, the key-type retainer, bands or sling-type retainers.